Abstract

Media summary

Keywords head

Rice, wheat, maize, permanent bed, straw retention, nitrogen

Introduction

Land degradation and the deterioration of soil fertility are among the main causes of the stagnation or decline of agricultural production in many tropical countries. Approximately 85% of rice-wheat system is practiced in the Indo-Gangetic Plains of South Asia in India, Pakistan, Nepal and Bangladesh (Timsina and Connor 2001). Rice is planted in damp and flat soils after thorough plowing, which negatively affects soil properties (Hobbs and Giri 1998). Wheat is then planted in these degraded soils. Change from growing crops on the flat to planting crops on raised beds offers more effective control of irrigation and drainage in addition to increased nutrient uptake and efficiency as well as rain water management during the monsoon season. Connor et al (2003) reported that permanent raised beds may offer farmers significant advantages, such as reduced tillage, increased opportunity for crop diversification, mechanical weeding and placement of fertilizers, opportunities for relay cropping and intercropping, and water savings. There are also indications that crop yields from beds can be further increased with higher N doses and later irrigation because of the reduced risk of lodging (Sayre and Ramos 1997). Raised beds are widely used in developed countries but have been introduced only recently in Bangladesh to improve system productivity (Talukder et al 2002). Crop residues are an important natural resource in the stability of agricultural ecosystems. About 25% of N and P, 50% of S and 75% of K uptake by cereal crops can be retained in crop residues, making them valuable nutrient sources (Singh 2003). Traditionally, in rice-wheat or other systems of South Asia, straw is fed to cattle, burned for fuel, or used as building material leaving little for soil incorporation. As a result soil organic matter levels are declining in these cropping systems which can have serious implications for soil health. These factors, along with N fertilization, must be considered to develop new farming practices that can increase system yields. Investigations were undertaken on permanent bed systems to: (i) evaluate yields of multi crops and (iii) study the profitability of the pattern, as affected by N levels and straw management.

Methods

A wheat (Triticum aestivum L.)-summer maize (Zea maize L.)-monsoon rice (Oriza sativa L.) cropping pattern during 2001-02, 2002-03 and 2003-04 seasons was studied at the Wheat Research Centre, Dinajpur, Bangladesh (25⁰38' N, 88⁰41' E, and 38.2 m asl). The experimental soil had low organic matter (0.8 %) and low nitrogen [Total N (35µg/g soil)]. The soil was sandy loam and acidic in nature (pH 5.5). The study was designed in a split plot with three straw management practices (straw removed, and 50% and 100% straw retention) as the main plots and four N levels (0, 50, 100 and 150% of recommended) in sub-plots, all on permanent raised beds. In straw removed treatment, straw of all crops was removed. The beds reshaped with little tillage prior to planting of each crop.

The width of the bed was 75 cm. Two rows of wheat (var. Kanchan), or rice (var. BRRI Dhan 32), and 1 row of maize (var. Pacific 11) were planted on the top of each bed during the respective crop seasons. The mungbean (var. BARI Mungbean-5) was sown on the furrows between the maize beds as a bonus and indicator plant to see the microbial activities in the soil environment. Mungbean was harvested in about 65 days after seeding. The space between wheat and rice row on the bed was 30 cm. Rice and maize were planted with a spacing of 30cm x 20cm and 75cm x 25cm, respectively. Chemical weed control in all crops was administered 1 or 2 days before planting through the application of 1.4 kg a.i./ha glyphosate [N-(phosphonomethyl)glycine]. Manual weed control was done after the first irrigation for wheat, 45 days after planting for maize and rice, and 25 days after planting for mungbean. All crops were harvested by cutting a 7.5 m² portion at the center of each micro-plot. Finally, grain yields were adjusted to 155 g/kg moisture for maize and 120 g/kg for others. Soil and plant samples were also taken for N-uptake calculation. Data were analyzed for variance (ANOVA) by using MSTAT-C. Treatment means were compared using Duncan’s Multiple Range Test (DMRT) at P ≤ 0.05. The partial budget and marginal analysis of undominated treatment responses of pooled yield were done by the method of Elias and Karim (1984).

Results

Table 1 shows that weed infestation was reduced due to retention of straw. Straw covered the soil surface and hence may have prevented weed seed germination. An initial light pre-seeding irrigation stimulated emergence of weeds, followed by their control with non-selective herbicides.

Table 1: Total weed (#/m²) infestations in various crops as influenced by straw retention in rice-wheat-maize cropping system in permanent beds (2002-03 to 2003-04)

^¶NL= narrow leaf, BL= broad leaf

Table 2: Grain yields (t/ha) of various crops (two years pooled) as influenced by straw management and N levels in a rice-wheat-maize cropping system on permanent beds.

^¶Within the treatment interactions the figures having the same letters are not significantly different at 5% level by DMRT.
^‡ Numbers in parentheses represent percentage increase over straw removal.
^† Numbers in parentheses represent percentage increase or decrease in grain yield over 50% straw retention.

Retention of straw was important in achieving higher yields and increasing system productivity. Table 2 shows that the 50% straw retention plus 100% N treatment had a 32% increase in maize grain yield over straw removal at the same N rate. Maize yields from 50% and 100% straw retention at both 100% and 150% N rates were higher than the other N and straw treatments but not statistically different from each other. Subsequent rice yield also increased significantly by 33% with 50% straw retention plus 100% N rates over straw removal. There were no significant differences between 50% or 100% straw retention with 50 or 150% recommended N rates. The maximum grain yield of wheat (5.03 t/ha) was obtained from 50% straw retention plus 150% N rates, which was 26% higher compared to straw removed plots. Yield decreased by 8% with 100% straw retention compared to 50% retention under 150 kg N/ha N in wheat. These yield increases with straw retention may be due to the conservation of soil moisture, less weeds, and more efficient use of fertilizers. Limon-Ortega et al (2000) reported that permanent beds combined with retaining all crop residues in the soil as stubble have the potential to increase both wheat and maize yields with higher nitrogen management.

Economic analysis was done to find out the best straw and nitrogen dose combination that gives more economic benefit as well as higher yield. Marginal analysis, under partial budgeting systems, was done to find out economically the most profitable treatment. The costs that vary from treatment to treatment like quantity of straw and nitrogen level and labor for applying fertilizer, straw mulching and weeding were considered as variable costs. Other costs such as fertilizers, seeds and seeding, irrigations, etc. were assumed same and the existing market price was considered for the analysis. The marginal analysis of non-dominated cost treatments showed that the marginal rate of return (MRR) on investment was highest (1945%) for 50% straw retention plus 50% recommended N treatment, followed by 50% retention plus 100% N (1236%) (Table 3). The use of 50 or 100% recommended N with 50% straw retention optimized the yield and maximized the profit.

Table 3: Economic analysis of various treatments on permanent beds.

^¶1US$=60 Taka; SR, Straw retention; N, % of recommended

Conclusion

Use of crop residues is an important component of soil restorative management, and may have a long-term positive impact on soil quality. Retention of crop residues may influence on soil organic matter content and moisture depletion. Fertilizer use efficiency may be increased with a change to permanent bed management and less problem of weeds and crop lodging. Raised beds also provides a means to help ameliorate the adverse effects of tillage and excess water leading to waterlogged conditions that hamper growth and development of most crops. The use of permanent beds reduced cost of production and long turn-around time with more economic gains. Permanent bed with 50% straw retention of previous crops in combination with use of 50-100% N fertilizer results in high yield and profit.

References

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Improving the Productivity and Sustainability of Rice–Wheat Systems: Issues and Impacts. ASA Special Publication 65, 197-210.

Elias SM and Karim R (1984). Application of partial budget technique in cropping system research at Chittagong. AEER No.1. Agriculture Economics Division, BARI, Gazipur, 75-81.

Hobbs PR and Giri GS (1998). Reduced and zero-tillage options for establishment of wheat after rice in South Asia. In HJ Braun (ed), Wheat: Prospects for Global Improvement. Dordrecht: Kluwer Academic Press.

Limon-Ortega A, Sayre KD and Francis CA (2000). Wheat and Maize Yields in Response to Straw Management and Nitrogen under a Bed Planting System. Agron. J. 92, 295-302.

Sayre KD and Moreno Ramos OH (1997). Application of Raised-Bed Planting System to wheat. Wheat Special Report no. 31. Mexico, DF:CIMMYT.

Singh Y (2003). Crop Residue Management in Rice-Wheat System. RWC-CIMMYT (2003). Addressing Resource Conservation Issues in Rice-Wheat Systems of South Asia: A Resource Book. Rice-Wheat Consortium for the Indo-Gangetic Plains-CIMMYT, New Delhi, India 153.

Talukder ASMHM, Sufian MA, Meisner CA, Duxbury JM, Lauren JG and Hossain ABS (2002). Rice, wheat and mungbean yields in response to N levels and Management under a Bed planting system. Proceedings of the 17th World Congress of Soil Science, Bangkok, Thailand. Vol no.1. Symposium no. 11, 351.

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